After reading everyone's great advice, I'm thinking about spending the last two nights of our trip in Amboise (at either Chateaux des Ormeaux or Manoir les Minimes). We'd like to do the usual site seeing while in Amboise. Would folks recommend renting a car in Paris and driving to Amboise, keeping the car for our site seeing and then returning it at the airport when we leave? The other option would be to take the train to Amboise from Paris, find local transportation to take us to the sites and then take the train back to the airport.
Again...appreciate the help. You folks are amazing!

I vote car. We obtained our car from CDG and drove to Esvres-sur-Indres (a bit west of Amboise) by way of Chartres. Having a car whilst in the Loire made for easy daytrips, as well as the option of going out-of-the-way for dinners, etc.

Or take the train from Gare Montparnase to St Pierre des Corps and rent a car. The agencies have offices in the station, and the cars are close by in the lot.

You need a car to really get the most out of your visit to Amboise and surrounds, since most Chateaus are not near or on public transport, and private "van tours" etc add up, renting a car may be the smartest move.
Hope you can drive a standard, they are cheaper to rent.
I can't advise re renting car arrangments, we have a car when we are in area, but we borrow it from relatives.

Unless you're planning to limit your sightseeing in Amboise only, you'll need a car. Alternatively, I suppose there are tours you can join in Amboise that will take you to visit the chateaux.

You can either rent a car from Paris and return it at the airport.

Alternatively you can take the TGV to Tours (stop is St Pierre-des-Corps) where you can rent a car. Afterwards, you can return your car there and take the TGV to CDG.

I agree with the previous posts about renting a car.

Getting to whichever châteaux you desire from Amboise would be much easier that way than by train, although we biked from Amboise to Chenonceau, but to get to any of the other châteaux...hiring a local might be the only way without a car.

Two other notes:

1. The Manior les Minimes was tremendous although we have never stayed at the Chateaux des Ormeaux for comparison purposes. The location is great...so close to everything.

2. A great dinner idea in Amboise is at the du Lys...

Here is link to some other thoughts on this place:

http://www.tripadvisor.com/ShowTopic-g187116-
i3457-k267670-Pavillion_des_Lys-Amboise_Loire_Valley_
Centre.html

Photos from the Manior les Minimes can be found at:

http://www.flickr.com/photos/timjstark/sets/645052/

Amboise is a great town!

You don't need a car for Amboise only - it's very walkable.

M. les Minimes was just right, with enclosed parking and just of the 'D' road for easy in/out of Amboise.

We rented from AVIS at St Pierre des Corps.